The present invention relates to vehicle navigation systems. More specifically, the invention relates to the use of directional arrows displayed on vehicle navigation systems and associated with directions of travel to destinations.
Vehicle navigation systems have become more prevalent in recent times. Typically vehicle navigation systems employ a map database wherein information such as digitized road segments, points of interest, landmarks, and similar location data is stored. Some vehicle navigation systems use Global Positioning Sensors to determine the vehicle""s location and compare the sensor data with the stored digitized map data. The degree to which road information is digitized varies considerably in different geographical areas. For instance, in a sparsely populated state or region, only roads of a high level in the road hierarchy might be digitized and stored in a map database. Densely populated regions, such as portions of the State of California, might have the vast majority of roads large and small stored in the map database. Even then, occasions may arise when the vehicle is located on a road which does not appear in the map database.
Vehicle navigation systems will include an output display to convey navigation information to the user. The output may take the form of maneuver instructions, a route map, a directional arrow or typically a combination of these features. The directional arrow, for example, will point in the direction from the vehicle""s present location to the destination. Typically the displayed directional arrow will be dynamically updated to continuously adjust the direction of the directional arrow for changes in position and direction of the vehicle, whether it is traveling along a calculated route, departing from the route, or even located on a road not appearing in the digitized map database. The navigation system produces this directional data necessary for the display of the directional arrow after comparing the latitude and longitude coordinates of the vehicle""s present location with coordinates of the destination as stored in the map database. Navigation by use of the directional arrow is an iterative process with the directional arrow constantly providing a visual display of the corrective action required by the driver to reach the desired destination. Ideally, the directional arrow will be pointed in the 12:00 position, indicating a convergence between the vehicle heading and the direction to the desired destination. For example, a directional arrow pointing in a 3:00 position would advise the driver that in order for the vehicle to be headed to the destination, a 90 degree turn to the right would be required. The use of directional arrows has, however, created certain problems.
One problem occurs when using the directional arrow in a non-digitized area. For example, one vehicle navigation system upon startup compares the vehicle""s present location with the map database. If no match is made, the system display indicates the direction to the destination with an arrow. Under this system the updated directional arrow will provide the sole navigation guidance to the user until the vehicle""s present location coincides with a road segment stored in the map database. While the directional arrow can be helpful to the user, in many instances the information can be misleading. FIG. 1A shows an instance where this directional method would be of little use to the user. A vehicle located at location 102, perhaps in a rural area of Nevada on an undigitized road segment might intend to travel to a destination 104 in the Los Angeles area and be prompted with a directional arrow 106 pointing in a southwesterly direction. The problem with the directional arrow in this instance is that it would lead the user further into remote areas and away from the nearest major highway which might be east-west oriented Interstate Highway 80, even if the highway was only a few miles away. What is needed, therefore, is a method of using a directional arrow to direct a user to a more meaningful intermediate location when a vehicle is on an undigitized road segment.
A second problem experienced by vehicle navigation system users relying on directional arrows occurs when the vehicle is traveling along a calculated route in a direction contrary to the directional arrow. This divergence in directions occurs when the calculated route provides, at least on a temporary basis, a circuitous route to the destination. This situation can frequently occur when the geographical features of the region such as hills, mountains, rivers, lakes, oceans, etc. prevent a more direct routing to the destination. The divergence between the direction of travel and the direction to the destination can cause confusion to the user, thereby raising questions in the user""s mind as to whether the navigation system is operating properly. FIG. 1B illustrates the problem as it would occur in a vehicle traveling along the California coastline 120. A vehicle located at position 122 near Santa Cruz and headed towards a destination 124 in Monterey would confront a directional arrow 128 pointed in a southerly direction, yet the vehicle heading 126 along the calculated route would be in an easterly direction. The opportunity for confusion in this instance would be especially great since the directional arrow 128 would be pointing directly into the Pacific Ocean. What is needed in this instance is again a more meaningful directional arrow so that the driver avoids confusing situations where the directional arrow is pointing in a significantly different direction than the vehicle heading, even though the vehicle is appropriately traveling along the calculated route.
Yet another problem facing the users of vehicle navigation systems and directional arrows occurs when the vehicle, traveling on a route generated by the navigation system, departs from the calculated route and attempts to use the directional arrow to navigate to the destination. Problems such as traffic congestion, highway construction, and detours might compel a user to depart from the calculated route to avoid traffic. Other circumstances giving rise to such a situation include voluntary departures from the route to visit a point of interest or landmark and general attempts by drivers to find shortcuts, irrespective of the traffic conditions on the calculated route. Even after the vehicle had departed from the calculated route, the directional arrow appearing on the display under present systems still would lead the user to the final destination. The problem with this approach is that even though it might be far more efficient to get back onto the calculated route immediately after passing the congestion or bottleneck, the directional arrow may direct the user away from the best point of access to the original route. FIG. 1C illustrates the problems inherent in such a situation. A vehicle at location 140 on eastbound Highway 280 near San Jose traveling to destination 142 near Santa Cruz may opt to depart from the calculated route to avoid a traffic accident or congestion at location 144. Once off of the calculated route at location 146 on road segment 148, the vehicle navigation system maneuver instructions would provide no assistance to the driver in navigating to the destination. In similar fashion, the directional arrow 150 would provide little assistance to the driver since it would be pointing only to the final destination 142 near Santa Cruz in a general direction where there may be an absence of roads or alternately only secondary level or unimproved roads. What is needed is a directional arrow which will provide more useful directional indications in such a situation.
The present invention provides methods and apparatus for generating directional indicators on vehicle navigation displays. To achieve the foregoing, the present invention provides a directional arrow on a vehicle navigation system display to assist a driver in driving to a destination. In cases where the vehicle is not at a location matching a road segment in a map database of the system, the directional arrow points to a nearest road segment from the map database instead of the destination. This proves to be useful when the vehicle location is in a rural area and the direction to the destination is away from the nearest road segment. In another aspect of the present invention, the display provides a directional arrow to one or more intermediate locations along the route calculated by the system. This can assist drivers who choose to depart from the calculated route to avoid congestion along the route from traffic, construction, or other delays or when the vehicle is traveling on a winding road.
According to one aspect of the present invention, a vehicle navigation system is provided and includes a processor configured to determine the vehicle location from location data generated by a plurality of sensors. Where the location data does not correspond to map data in a map database, a directional indicator is generated on the display to indicate a first location corresponding to the map data. In one embodiment, the first location corresponds to a road segment in the map database nearest the vehicle location. In another embodiment, the processor is configured to identify an intermediate location on the route and generate a directional indicator on the display which indicates the direction to the intermediate location. In yet another embodiment, the processor is configured to monitor an angle between a current vehicle heading and a directional indicator corresponding to a first location associated with a route. When the angle exceeds a threshold, the directional indicator displayed corresponds to an intermediate location.
Computer implemented methods for navigating using a vehicle navigation system are also provided.